Itchgrass

Coarse annual. Culms stout, 1–3 m tall, 5–10 mm in diam., supported below by stilt roots, branched in upper part. Leaf sheaths tuberculate-hispid with stiff irritant hairs or sometimes glabrescent; leaf blades linear-lanceolate, 20–50 × 0.5–2.5 cm, glabrous or adaxial surface hispidulous, very scabrid along margins, midrib broad, white, apex acuminate; ligule a ciliate membrane, ca. 1 mm. Racemes yellow and green, 6–15 × 0.25–0.4 cm, stiff, terminating in a green tail of reduced spikelets; rachis internodes 4–6 mm, rounded on back, slightly longer than adjacent pedicel. Sessile spikelet pale yellow, 5–6 mm; lower glume ovate, minutely scaberulous on back, keeled only toward entire or very minutely 2–3-toothed apex; lower lemma as long as upper lemma. Pedicelled spikelet green, variable, 3–5 mm, narrowly ovate, herbaceous. Fl. and fr. Jul–Oct.

Fujian, Guangdong, Guang-xi, Guizhou, Hainan, Hunan, Sichuan, Taiwan, Yunnan, Zhejiang [throughout the Old World tropics; introduced to the Caribbean].

Sunny or moderately shady localities, roadsides, hill thickets, dry cultivated fields, grasslands; below 1900 m.

Stegosia cochinchinensis Loureiro, Fl. Cochinch. 51. 1790; Rottboellia exaltata Linnaeus f. (1781), not (Linnaeus) Linnaeus f. (1779).